Method and apparatus for determining metabolic characteristics of experimental animals

ABSTRACT

A method for electronically determining a metabolic characteristic of an experimental animal in a living space is disclosed. The method includes confirming that a temperature in a living space is within a predefined range that consists of temperatures near or within a metabolic thermoneutral zone of the experimental animal, capturing at least one infrared image of at least one experimental animal in a band of infrared radiation that is within the range of from about 3 μm to about 14 μm in wavelength, identifying at least one data set of the at least one infrared image that corresponds to a tail of the experimental animal, processing the at least one data set of the at least one infrared image to evaluate a temperature of the tail of the experimental animal, and determining the metabolic characteristic based at least in part on the evaluated tail temperature.

TECHNICAL FIELD

This application relates to methods and apparatuses for facilitatinganimal research.

BACKGROUND

Research is commonly performed on experimental animals that are housedin cages. Typically, these experimental animals are small mammals, suchas mice or rats. The research may involve, for example, a drug test, anutritional test, a genetic test, a test of a surgical procedure, anoptogenetics test, or another observation of a physiological orbehavioral response to a change in environmental condition or otherstimulus. The experimental animals may be divided into a control groupand one or more experimental groups. The cages in which the animals arehoused may be arrayed, such as in racks.

The housed animals are typically checked in at least two ways: husbandrychecks and experimental checks. Husbandry refers to serving thephysiological needs of the animals. Husbandry may include observing thewellbeing of the animals, such as, for example, a health check once ortwice a day to make sure that none of the animals has developed anysymptoms of disease or has died. Health checks may involve looking atthe animals through the transparent cage walls in situ without movingthe cages, or alternatively pulling the cages partially or completelyout of their racks to visually inspect the animals. Experimental checks,meanwhile, are performed to obtain data for the research beingconducted. Experimental checks may involve closer examination of theanimals than husbandry checks, such as involving opening the cages andremoving the animals from the cages. Experimental checks may involve,for example, looking for clinical symptoms in the animals. Experimentalchecks may also include behavioral tests, such as, for example, watermaze or hole board tests, extractions of blood or tissue from theanimals, or measurements, such as imaging of the animals.

However, physically contacting the animals, such as through opening theanimals' cages, removing them from their cages, and performingmeasurements on them—or even just approaching the cage to view theanimal through the bidirectionally transparent wall, or partiallysliding the cage containing the animal out of a rack—can physiologicallyor psychologically perturb the animals. The consequences of these typesof perturbations are often not well understood. Furthermore, there maybe inconsistencies in the perturbations, such as differences in when andhow the human technicians perform checks across different individualanimals. The animals' physiological states and behavior may therefore bealtered in ways that are difficult to predict and inconsistent betweendistinct animals. Thus, these measurement techniques can interferesignificantly with the quality of the data obtained from the experiment.

The process of checking the experimental animals may also causecontamination of the animal's living space or the testing equipment.This contamination may, in turn, exacerbate the differences inconditions under which the animals are housed. For example, one humantechnician may introduce one particular foreign odor into one livingspace, while another human technician introduces a different odor intoanother living space. The human technicians who are handling animalsfrom different cages, or using common equipment, may also causecross-contamination between animals in different cages. In addition, asubstantial amount of resources, such as the time and labor of skilledtechnicians, is expended to monitor the animals. This can account for asignificant amount of the total cost of running such an experiment.

Thus, it is desirable to perform checks on experimental animals toexperimental animals in a way that yields rich, high-resolution, andreliable data in relation to the number of animals. It is also desirableto avoid physical contact with the animals, inconsistent perturbationsof the animals, and cross-contamination between animals in differentcages when the animals are checked. Moreover, it is desirable to reducethe amount of time and labor that is expended on running animalexperiments.

Thus, it would be desirable to have processes and systems to determinephysiological characteristics of experimental animals without or withminimal human technician effort, time, and handling and/or directobservation of experimental animals. It would be desirable for suchprocesses and systems to be efficient, reproducible, and/or relativelyinexpensive.

Experimental animals may be monitored, at least in part, by variousimage capture devices within or outside cages. However, providing imagecapture devices within cages presents potential issues regardingpossible contamination of, decreased lifespan of, and/or increasedrepair or maintenance such image capture devices. And, providing a setof image capture devices for each cage may be expensive, decreasing theeconomic efficiency of monitoring experimental animals via image capturedevices en masse. Furthermore, certain plastic and other type of cagescommonly used to house and monitor experimental animals may includewalls that are transparent to visible light, but not transparent toinfrared light.

Thus, it would be desirable to have experimental animal cages andmonitoring systems that are, at least in part, transparent to infraredlight, while at the same time are efficient to use, reproducible, and/orrelatively inexpensive.

SUMMARY

In one embodiment, a method for electronically determining a metaboliccharacteristic of an experimental animal in a living space is provided.The method includes confirming that a temperature in a living space iswithin a predefined range that consists of temperatures near or within ametabolic thermoneutral zone of the experimental animal, capturing atleast one infrared image of at least one experimental animal in a bandof infrared radiation that is within the range of from about 3 μm toabout 14 μm in wavelength, identifying at least one data set of the atleast one infrared image that corresponds to a tail of the experimentalanimal, processing the at least one data set of the at least oneinfrared image to evaluate a temperature of the tail of the experimentalanimal, and determining the metabolic characteristic based at least inpart on the evaluated tail temperature.

The predefined range may consist of temperatures within about 2° C.,about 1° C., and/or about 0.1° C. of the metabolic thermoneutral zone ofthe experimental animal. The predefined range may consist oftemperatures within the metabolic thermoneutral zone of the experimentalanimal, about 27° C. to about 28° C., about 28° C. to about 29° C.,and/or about 29° C. to about 30° C. The predefined range may consist oftemperatures within about 1° C. or 0.5° of a lower critical ambienttemperature of the metabolic thermoneutral zone of the experimentalanimal.

Identifying at least one data set of the at least one infrared imagethat corresponds to a tail of the experimental animal may furtherinclude determining a position of the tail within the living space andcorrelating the position of the tail with the at least one infraredimage. Determining a position of the tail within the living spacefurther may further include capturing at least one visible image of theat least one experimental animal and processing the at least one visibleimage using one or more computer vision techniques to determine theposition of the tail.

The method may further include heating the living space to cause thetemperature in the living space to be within the predefined range.

The living space may further include a temperature reference point. And,confirming the temperature of the living space may further includedetermining a position of a temperature reference point within theliving space, capturing at least one infrared image of the temperaturereference point in a band of infrared radiation that is within the rangeof from about 3 μm to about 14 μm in wavelength, correlating thedetermined position of the temperature reference point with the at leastone infrared image to determine the temperature of the living space.

The method may further include measuring a core temperature of theexperimental animal and calculating a difference between the coretemperature and the tail temperature. Determining the metaboliccharacteristic based at least in part on the tail temperature mayfurther includes determining the metabolic characteristic based at leastin part on the calculated difference between the core temperature andthe tail temperature.

Measuring the core temperature of the experimental animal may furtherinclude measuring an eye temperature of an eye of the experimentalanimal. And, measuring the eye temperature may further includedetermining a position of the eye of the experimental animal within theliving space and correlating the determined position of the eye with theat least one infrared image to determine the eye temperature.Determining the position of the eye within the living space may furtherinclude capturing at least one visible image of the at least oneexperimental animal and processing the at least one visible image usingone or more computer vision techniques to determine the position of theeye.

The method may further include administering a chemical compound to theexperimental animal.

In another embodiment, a method for electronically determining ametabolic characteristic of an experimental animal in a living space isprovided. The method includes capturing at least one infrared image ofat least one experimental animal in a band of infrared radiation that iswithin the range of from about 3 μm to about 14 μm in wavelength,measuring a core temperature of the experimental animal using the atleast one infrared image, measuring a temperature of a tail of theexperimental animal using the at least one infrared image, calculating adifference between the core temperature and the tail temperature, anddetermining the metabolic characteristic based at least in part on thecalculated difference.

The method may further include maintaining a temperature of the livingspace within a predefined range that consists of temperatures near orwithin a metabolic thermoneutral zone of the experimental animal.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate several embodiments and aspectsof the apparatuses and methods described herein and, together with thedescription, serve to explain the principles of the invention.

FIGS. 1A and 1B are front and perspective views, respectively, of anexample of an embodiment of a cage with a thermographically transparentwindow.

FIGS. 2A and 2B are front and perspective views, respectively, of anexample of another embodiment of a cage with a thermographicallytransparent window.

FIG. 3A is a front view of an example of the cage embodiment of FIGS. 1Aand 1B connected to an electronic monitor.

FIG. 3B is a front view of the cage embodiment of FIG. 3A, in which twoimage capture devices are aligned with the thermographically transparentwindow.

FIG. 4 is a flowchart of an example of a method of determining at leastone physiological characteristic of an experimental animal.

FIGS. 5A and 5B are a pair of corresponding infrared and visible lightimages, respectively, of an experimental animal in a cage, consistentwith disclosed embodiments.

FIGS. 6A and 6B are another pair of corresponding infrared and visiblelight images, respectively, of an experimental animal in a cage,consistent with disclosed embodiments.

FIGS. 7A to 7G are corresponding infrared and visible light images andannotations thereupon that illustrate identification of a position ofparts of an experimental animal and determination of a temperature ofsuch parts, consistent with disclosed embodiments.

FIG. 8 is a schematic illustration of a side view of an example of anembodiment of a cage connected to an electronic monitor with a set ofimage capturing devices.

FIG. 9 is a flowchart of an example of a method of determining at leastone metabolic characteristic of an experimental animal.

DETAILED DESCRIPTION

An electronic monitor may be adapted to be removably coupled to a cagehousing experimental animals to be positioned in a predefined positionrelative to the cage and monitor one or more of the experimentalanimals. The electronic monitor can be adapted to maintain asubstantially sterile barrier between the animal living space in thecage and the environment external to the cage while the electronicmonitor is coupled to the cage. Sterility refers to chemical andbiological isolation from the ambient environment, such as, for example,isolation from foreign odors, soot particles, viruses, parasitic wormeggs, bacteria, prions, proteins, metabolites, parasitic mites and theireggs, and humidity and temperature fluctuations. The electronic monitorcan thereby monitor the experimental animals while minimizingperturbations to the animals. Examples of such an electronic monitor andother related experimental animal monitoring instrumentalities aredescribed in U.S. patent application Ser. No. 14/549,403 toBetts-LaCroix et al., U.S. patent application Ser. No. 14/788,749 toHeath et al., and U.S. patent application Ser. No. 14/871,966 toBetts-LaCroix et al., which are incorporated herein by reference intheir entireties.

Multiple animals that are under the same experimental conditions may beselected to be housed in the same cage. For example, animals in acontrol group may be housed together, while animals in a particularexperimental group may be housed together. When animals that are underthe same experimental conditions are housed in the same cage, it may notbe necessary for electronic monitor 200 to track the individualidentities of the animals, though that is also contemplated by thisdisclosure. Rather, since the mice may be treated as experimentallyidentical, aggregated or averaged information relating to all of themice in a particular cage may suffice for purposes of the experiment.

FIG. 3A illustrates an example of an embodiment of an electronic monitor200 and a cage 100 that is coupled thereto. Cage 100 has one or morewalls 110 that enclose a living space for experimental animals. In oneembodiment, walls 110 define a living space that is approximately arectangular prism. In other embodiments, however, walls 110 may haveother shapes or dimensions. In illustrative examples, a mouse cage maybe shaped and sized to house from one to about five mice, while a ratcage may be capable of housing up to about 10 mice. For example, micemay be housed singly or in pairs. In one embodiment, walls 110 of cage100 enclose a substantially cuboid living space 145 of at least 10 cm×10cm×5 cm. In various embodiments, cage 100 may have a volume less that 60liters, less than 20 liters, and/or less than 10 liters. In variousembodiments, wall 110 may have a thickness of less than 0.1 mm, 0.25 mm,0.1 mm to 0.5 mm, 0.5 mm to 5 mm, and/or more than 5 mm. While thinnercages may be lighter and cheaper, thicker cages may be stronger and morerobust. Cage 100 may comprise or consist essentially of a plasticmaterial or materials, for example, Polycarbonate, PET, PETG,Polystyrene, Polypropylene, Polysulfone, or alloys, derivatives, orcopolymers based on the same.

Cage 100 may further comprise cage floor 115 and one or more protrudinglip 111. By one or more lip 111 of cage 100 and one or more supportflanges 211 of electronic monitor 200, cage 100 may be securely coupledto electronic monitor 200. Electronic monitors 200 may be structurallyadapted to permit easy and fast uncoupling of cages 100 from electronicmonitors 200 by a human technician or even by a robot. For example,electronic monitors 200 may be structurally adapted to permit couplingand uncoupling by sliding cages 100 into and out of electronic monitors100. To that effect, via protruding one or more lip 111 and one or moresupport flanges 211 of electronic monitor 200, cage 100 may be securelymounted within electronic monitor 200.

Cage 100 may also include shaped features to provide water and/or foodto the experimental animals. For example, cage 100 may have a waterdispenser and/or a food dispenser. If cage 100 is of a disposable type,then water dispenser and/or food dispenser may be pre-filled with anamount of water or food corresponding to an expected lifespan of theanimals, an expected timespan of an experiment, or a given intervalbetween cage changes. A given interval between cage changes may be, forexample, one, two, or four weeks, such as may be suitable for theparticular types of cage, animal, and experiment.

As depicted in further detail in FIGS. 1A and 1B, at least one wall 110of cage 100 may include at least one window 120. In exemplaryembodiments, window 120 may be thermographically transparent such thatthermographic images may be captured through it. For example, window 120may be transparent to a band of infrared radiation that is within therange of from about 3 μm to about 14 μm in wavelength. In other words,window 120 may be substantially transparent to wavelengths betweenapproximately 3 μm and approximately 14 μm. Window 120 may, in someembodiments, may include or consist essentially of ZnCl or NaCl. Inexemplary embodiments, at least the inner side of window 120 that isexposed to the living area of cage 100 comprises a non-toxic material,such as NaCl. In other exemplary embodiments, at least the inner side ofwindow 120 may be covered with a hard carbon coating such as the“Diamond-Like Coating” produced by Tydex. Use of a non-toxic materialmay prevent adverse health effects and/or compromised experimental dataif an experimental animal ingests some the window 120 material. Further,use of a non-toxic material on the inner side of window 120 may permitwindow 120 to substantially consist of a lower cost material. In variousembodiments, window 120 may have a thickness of less than 0.1 mm, 0.25mm, 0.1 mm to 0.5 mm, 0.5 mm to 5 mm, and/or more than 5 mm.

Wall 110 may include an aperture 125 covered by window 120 such thatinfrared light may pass through that portion of wall 110. In variousembodiments, aperture 125 may be integrally formed during molding ofcage 100, or may be created via punching, drilling, melting, sanding, orthe like of a portion of wall 110. For example, as shown in FIGS. 1A and1B, the surface area of window 120 may be greater than the size ofaperture 125. In this manner, window 120 may be secured to the portionof wall 110 surrounding aperture 125. In embodiments where window 120 ispositioned on the outside surface of wall 100 (e.g., outside the livingarea), an outer portion of the inner surface of window 150 (e.g., facingthe living area) may affixed to portions of the outer surface of wall110 with an adhesive material, such as a non-toxic glue. The portions ofthe outer surface of wall 110 to which window 120 is affixed may be aplastic material. Conversely, in embodiments where window 120 ispositioned on the inside surface of wall 100 (e.g., inside the livingarea), an outer portion of the outer surface of window 150 (e.g., facingaway from the living area) may affixed to portions of the inner surfaceof wall 110 with an adhesive material, such as a non-toxic glue. Theportions of the inner surface of wall 110 to which window 120 is affixedmay be made of a plastic material.

With reference to FIGS. 2A and 2B, window 120 may be fitted at leastpartially within aperture 125. Window 120 may be maintained withinaperture 125 via interference fit and/or an adhesive material.

FIG. 3B depicts the system of FIG. 3A, but also includes camera system130. As shown, camera system 130 may include a thermographic infraredcamera 132 and a visible light camera 134. Cameras 132, 134 may beconfigured to capture still images and/or video images and may besupported by camera support 130. In embodiments where multiple cages 100and electronic monitors 200 are supported by a rack, camera support 136may be configured to move such that camera system 130 may be used tosequentially capture images of experimental animals in various cages 100within the rack. In other embodiments, each cage 100 or electronicmonitor 200 may correspond to a camera system 130. In some embodiments,visible light camera 134 may capture image(s) through a transparentportion of wall 110, for example a portion of wall 110 adjacent to orotherwise near window 120.

It is contemplated that window 120 be disposed within wall 110 at aheight to reduce or eliminate the likelihood that an experimental animalmay lick, touch, or otherwise contact window 120. Similarly, it iscontemplated that window 120 be positioned to provide an optimal viewingangle of experimental animals in cage 100 for image capture devices 132,134. Thus, with reference to FIG. 121, the bottom of aperture 125 may bea distance 121 from cage floor 115 of cage 100. In various embodiments,distance 121 may be at least 25 cm, at least 15 cm, or at least 6 cm. Itis also contemplated that window 120 be disposed within wall 110 in aposition sufficiently far from lip 111 and/or the top of wall 110 toprevent possible interference, mechanical or otherwise, between aperture125 or window 120 and electronic monitor 200. Thus, in variousembodiments, a distance from the top of aperture 125 may at least 5 cmfrom lip 111 or the top of cage.

FIG. 8 depicts an alternative embodiment of cage 100 and electronicmonitor 200 in which electronic monitor 200 includes an infrared camera132 and a visible light camera 134. In such embodiments, electronicmonitor 200 may accomplish the functions of camera system 130 describedabove. In such embodiments, a thermographically transparent window 120may be omitted from cage 100.

In yet other alternative embodiments, infrared camera 132 may beincluded within electronic monitor 200 and visible light camera 134 maybe positioned to view cage 100 and its contents through wall 110 withoutwindow 120. And in yet other alternative embodiments, visible lightcamera 134 may be included within electronic monitor 200 and infraredcamera 132 may be positioned to view cage 100 and its contents throughwindow 120. In yet other embodiments, one or more cameras 132, 134 maybe provided within cage 100; such cameras may, for example, transmitdata and receive power through one or more electrical feedthroughs, suchas those disclosed in U.S. patent Ser. No. 15/280,565, filed Sep. 29,2016, which is incorporated herein by reference in its entirety.

In yet other alternative embodiments, window 120 may be omitted andinfrared camera 132 may capture images through aperture 125. The escapeof experimental animals through aperture 125 may be prevented by, forexample, a high placement of aperture 125, making aperture 125 too smallfor the experimental animal to fit through, or blocking aperture 125with a protective lens or other element of infrared camera 132.

FIG. 4 is a flowchart of an exemplary embodiment of a method of usinginfrared camera 132 and visible light camera 134 to determine at leastone physiological characteristic of an experimental animal. Infraredcamera 132 and visible light camera 134 may be controlled by and mayprovide captured imagery to a controller 140. Infrared camera 132 mayfor example, may be configured to capture images based on a band ofinfrared radiation that is within the range of from about 3 μm to about14 μm in wavelength. This disclosure further contemplates that any othertype of suitable thermographic camera may serve as infrared camera 132.

Controller 140 may be adapted to largely or wholly automate theoperation of infrared camera 132 and visible light camera 134, as wellas control the movement of camera support 136. Controller 140 mayaccomplish the data processing steps discussed below, including but notlimited to any image processing, position-determining, calibration,temperature adjustment, calculation, lookup, interpolation, and/orphysiological or metabolic characteristic determining steps discussedherein.

Furthermore, controller 140 may serve other functions, as explained inthe patent applications incorporated by reference above (with respect to“controller 320” in such applications). For example, controller 140 mayfurther control the operation of electronic monitors 200, control userinterfaces to interface with a human supervisor, and/or interface withan external server or network. Controller 140 may automatically controlone or more aspects of operation of electronic monitor 200 and may beadapted to largely or wholly automate the operation of electronicmonitor 200. The controller may, for example, receive inputs from ahuman user, provide instructions to other components of monitor 200,perform processing of data received from any or all of ambient sensors,atmospheric sensors, electromagnetic detectors, cameras 132, 134, acompound releasing system, acoustic sensors, and a weight scale, and/oroutput signals, such as alerts or other indicators. Controller 140 maybe adapted, for example, to receive signals from ambient sensors,atmospheric sensors, cameras 132, 134, other electromagnetic detectors,acoustic sensors 280, and weight scale; to transmit control signals toelectromagnetic sources 270 to provide electromagnetic radiation intothe living space; to transmit signals to an acoustic emitters; totransmit signals to user interfaces; or transmit and receive signals toa compound releasing.

Controller 140 may include one or more microprocessors, controllers,processing systems, computers, and/or circuitry, such as any combinationof hardware or software modules. Components of controller 140 may bedistributed across one or more different physical locations and thesecomponents may communicate with each other to perform the operations ofcontroller 140. For example, components of controller 140 may bephysically located in the individual electronic monitors 200 and/or atremote client devices such as personal computers or handheld devices.Controller 140 may be implemented in any quantity of hardwarecomponents, such as including Raspberry Pi, an integrated circuit suchas, for example, an application-specific integrated circuit (ASIC),field-programmable gate array (FPGA), or “system on a chip” (SoC),and/or other processor, memory, bus, input/output, or communicationssystems. Furthermore, some or all of these hardware components may belocated locally or remotely. For example, controller 140 may beimplemented partially or entirely through cloud computing. Controller140 may operate any commercially available operating system software,including, for example, Linux, Windows, MacOS, iOS, Android, Unix, OS/2,or any other commercially available and/or custom software. For example,controller 140 may operate customized animal-monitoring andsignal-processing software. Furthermore, controller 140 may include oneor more types of input devices, such as for example a touchpad,keyboard, button panel, mouse, microphone, or voice recognition device.

In some embodiments, controller 140 may govern disclosed processes withrespect to a single cage 100, in which case controller 140 may bedisposed within electronic monitor 200. In other embodiments, acontroller 140 may govern disclosed processes with respect to aplurality of cages 100, for example, a plurality of cages 100 supportedby a single rack or a plurality of cages 100 supported by a multipleracks in a single vivarium.

Controller 140 may be adapted to process received data and/or humaninputs to determine values of one or more metrics relating toexperimental animals or their living space. The metrics may include oneor more physiological, behavioral, or environmental characteristics.Physiological metrics or characteristics may include, for example,respiration rate, health check, heart rate, body weight, thinness, bodytemperature, metabolism, coat characteristics such as rough hair coat,stress level, a Body Condition Score (“BCS”), alopecia, fever,inflammation, arthritis, whether the animal is dead, ataxia or anothercentral nervous system (CNS) disorder, circling or head tilt,dehydration, dermatitis, distended abdomen, dyspnea, dystocia, earproblems, emaciation, eye problems, fight wounds, hunched posture,hydrocephalus, irregular gait, lesions, lethargy, listlessness,malocclusion, necropsy, the number of animals in a cage, paleness ofcolor, the presence of post-operative staples, prolapse, pruritus,seizure, other sickness, brown adipose tissue thermogenesis, metaboliccharacteristics, the presence of a tumor, and/or a degree of tumorvascularization.

As in step 410, an infrared image of an experimental animal may becaptured with infrared camera 132. The infrared image may be capturedthrough the side of cage 100, for example through a window 120 asdescribed above and depicted in FIG. 3B. In other embodiments, theinfrared image may be captured from above, for example from an infraredcamera 132 mounted within electronic monitor 200, as depicted in FIG. 8.FIGS. 5B, 6B, and 7B each provide an illustrative infrared image of anexperimental animal in a cage taken from above.

As in step 420, a visible light image of the experimental animal may becaptured with visible light camera 134. The visible light image may becaptured through the side of cage 100, for example through a window 120as described above and depicted in FIG. 3B. In other embodiments, thevisible image may be captured from above, for example from a visiblelight camera 134 mounted within electronic monitor 200, as depicted inFIG. 8. While it may be advantageous for visible light camera 134 andinfrared camera 132 to capture images from the same, adjacent (e.g., asshown in FIGS. 3B and 8), and/or or otherwise similar vantage points,embodiments where the cameras are located in disparate locations arealso contemplated. FIGS. 5A, 6A, and 7A each provide an illustrativevisible light image of an experimental animal in a cage taken fromabove, which correspond to FIGS. 5B, 6B, and 7B, respectively. WhileFIGS. 5B, 6B, and 7B each illustrate a zoomed-in or cropped infraredimage, it is contemplated the infrared image may depict a substantiallylarger portion of the cage, such as the subject matter shown in FIGS.5A, 6A, and 7A or the like. Further, it may be noted that the infraredimage of FIG. 7B has been adjusted to be at the same scale and rotationas the visible light image as FIG. 7A for illustrative purposes.

In some embodiments, the visible light image may be a visible lightvideo comprising multiple frames captured in sequence and/or theinfrared image may be an infrared video comprising multiple framescaptured in sequence. In other embodiments, the visible light image maybe a single frame of or a combination of multiple frames of a visiblelight video and/or the infrared image may be a single frame of or acombination of multiple frames of an infrared video.

In exemplary embodiments, the visible light and infrared images may becaptured substantially simultaneously, for example, within 0.25 seconds,0.1 seconds, or even 0.05 seconds of each other. In other embodiments,step 420 may occur prior to step 210. Further, in embodiments wherevideos are captured, a visible light video and an infrared video may becaptured substantially simultaneously.

As in step 450, the position of at least one part of the experimentalanimal may be determined. Computer vision processing techniquestechniques to identify an object, such as experimental animal, and aswell as specific parts of the animal are well known in the art. Anexperimental animal may be identified within an image through asegmentation process, whereby an image is divided into various portionsto identify a target object relative to a background, other stationaryobject, and/or other moving object, even when the lighting may bedynamic. For example, Branson, K. et al. Tracking Multiple MouseContours (Without Too Many Samples). 2005 IEEE Computer SocietyConference on Computer Vision and Pattern Recognition (CVPR '05),incorporated herein by reference in its entirety, teaches a method ofidentifying an experimental animal, even where multiple animals overlapin the same image. As another example example, Stauffer, C., and W. E.L. Grimson. “Adaptive Background Mixture Models for Real-time Tracking.”Proceedings. 1999 IEEE Computer Society Conference on Computer Visionand Pattern Recognition (Cat. No PR00149), incorporated herein byreference in its entirety, describes a method of segmentation.Additionally, Dalal, N., and B. Triggs. “Histograms of OrientedGradients for Human Detection.” 2005 IEEE Computer Society Conference onComputer Vision and Pattern Recognition (CVPR '05), incorporated hereinby reference in its entirety, describes a method of object recognitionbased on histograms that recognizes an object in various positions;although the references uses humans as an example, such method mayeasily be adapted to recognize experimental animals in variouspositions.

The determination of coordinates for parts of an object within an image,such as coordinates for an experimental animal's eyes, ears, tail, andpaws, are also well known in the art. For example, Viola, P. and Jones,M. “Robust Real-time Object Detection,” Cambridge Research LaboratoryTechnical Support Series, CRL2001/01, February 2001 (available athttp://www.hpl.hp.com/techreports/Compaq-DEC/CRL-2001-1.pdf),incorporated herein by reference in its entirety, utilizes an integralimage and a learning algorithm to quickly detect eyes as a key componentof facial recognition in humans; this may easily be adapted to detecteyes in images of experimental animals, such as mice. As used herein“eye” refers to the actual eye of an animal, but may also refer to thegeneral region of the eye, including the eye socket, as well as otherareas around the eye that are similar in temperature.

Additionally, the eyes of a mouse, or another experimental animal, havea set, predictable position with respect to other features of the mouse,such as the ears and nose. Identification of all of such features may bemade or confirmed based on their coloring (e.g., the ears and nose mayhave a pinkish hue), darkness, shape, size, and/or proximity ororientation vis-à-vis the other features. Similarly a tail may beidentified by its color; its position with respect to the identifiedexperimental animal (e.g., at the end of the body); and/or its curved orwinding shape, using, for example, the method histogram-based or machinelearning methods of Dalal and Viola referenced above. And, as may bevisible from images taken from the side of cage 100, paws may beidentified by color; their position with respect to the identifiedexperimental animal; and/or their particular shape, using, for example,the histogram-based or machine learning methods of Dalal and Violareferenced above. Ohayon, S. et al. (2013). Automated Multi-day Trackingof Marked Mice for the Analysis of Social Behaviour. Journal ofNeuroscience Methods, 219(1), 10-19, incorporated herein by reference intheir entireties, provide additional examples of body, head and tailidentification, including where markers are use. As examples, FIGS. 7Cand 7F depict, respectively, the identification of an eye and a tail ofan experimental animal.

The location of additional parts of an animal, for example,stereotypical locations for brown adipose tissue deposits such as theinterscapular area, or a tumor that is injected or grown, may bedetermined by reference to other identified parts. For example,coordinates for a brown adipose tissue deposit located in theinterscapular area may be determined by extrapolating a predictedlocation from the positions of the ears, eyes, and/or other more easilyidentifiable parts. Similarly, coordinates for a known tumor maydetermined by extrapolating a predicted location from the positions ofthe base of the tail, ears, eyes, and/or other parts.

Additionally, or alternatively, the infrared image may be used inidentifying the experimental animal and its various parts. For example,as can be readily observed from FIGS. 5B, 6B, and 7B, substantially theoutline of the body of a mouse and the outline of the mouse's ears mayhave as similar temperature, for example approximately 27-29° C., whichis typically elevated temperature when compared to the temperature ofthe background. The ears, nose, and base of tail may indicate a lowertemperature, for example approximately 24-27° C. The eyes are likely toindicate the highest temperature on the animal, for exampleapproximately 29-34° C. The paws may have a temperature of approximately22-36° C.

The coordinates may reference the position of at least one part of theexperimental animal in the visible light image, in the infrared image,and/or in a plane corresponding to a surface of the cage 100, forexample the cage floor 115 or wall 110, depending on the location ofcameras 132, 134. The coordinates may define an area of interest thatcorresponds to a plurality of pixels in the infrared image. Where both avisible light image and an infrared image are used to determine partposition, the images may be correlated with one another, as in step 455,discussed below, during or prior to this positioning determining step.That is, corresponding portions or elements of each image are mapped toone another.

If the identification of a particular part is sought and the part is notfound such that no coordinates may be determined, the process may startagain such that a more suitable set of images may be captured. Forexample, if identification of an eye of an experimental animal is soughtand the animal is facing directly away from the camera(s) at the time ofimage capture, the eye may be absent from the image(s) and therefore itmay not be possible to reliably determine the position of the eye.

In some embodiments, a distance of an experimental animal or its partsfrom visible light camera 134 and/or infrared camera 132 may bedetermined, for example, by comparing the area occupied by experimentalanimal within the image(s) to a predetermined area representative of theactual size of the animal. That is, the larger the area occupied byexperimental animal is with respect to the predetermined area, thecloser the animal may be to the camera(s). In some embodiments, thedistance may be estimated by taking a ratio these values andcross-referencing a lookup table or the like.

In some embodiments, angles of identified parts of the experimentalanimal with reference to visible light camera 134 and/or infrared camera132 may also be determined. First, a pose of the experimental animal inthe cage may be determined via methods well known in the art. Forexample, Wang, Chun-Kai. Multiple mice tracking using Microsoft Kinect.Diss. Massachusetts Institute of Technology, 2013 (available athttp://hdl.handle.net/1721.1/85517), incorporated herein by reference inits entirety, utilizes a statistical shape model and shape tracking toestimate the pose of a mouse. As another example, Xu, C. et al.“Estimate Hand Poses Efficiently from Single Depth Images.”International Journal of Computer Vision Int J Comput Vis 116.1 (2015):21-45, incorporated herein by reference in its entirety, discussesvarious methods by which poses of human hand gestures may be estimated;these methods may easily be adapted to detect the simpler poses ofexperimental animals. Then, once the experimental animal's pose isdetermined, the angle of the part of interest may be estimated based onan anatomy model of the experimental animal. For example, if thecamera(s) capture images though a wall 110 and if the animal's pose issuch that its head is pointed towards at a corner of the cage, a lookuptable may be used to approximate the angle of the eyes of theexperimental animal with respect to the camera(s). Indeed, well knownmethods for object detection are frequently applied to estimating thearticulated pose of non-rigid objects by simply learning many “partdetectors” (e.g., face, ear, hand, foot, elbow, shoulder) and fusing theresults with a object-specific geometric model (e.g., skeleton orconstellation model). For example, Bourdev, L et al. “Poselets: Bodypart detectors trained using 3d human pose annotations.” 2009 IEEE 12thInternational Conference on Computer Vision. IEEE, 2009 andFelzenszwalb, P. F., et al. “Object detection with discriminativelytrained part-based models.” IEEE transactions on pattern analysis andmachine intelligence 32.9 (2010): 1627-1645, incorporated herein byreference in their entireties, provide examples of such techniques.

Controller 140 may process the visible light image(s), the infraredimage(s), both, and/or other data to identify the experimental animal ina cage, identify one or more parts of the animal, and/or estimate theirrespective positions, including distance and angle with respect to thecamera(s).

As in step 455, the visible light image and an infrared image may becorrelated with one another. That is, corresponding portions or elementsof each image may be mapped to one another and/or both may be mapped toa plane corresponding to a surface of the cage 100. Where visible lightcamera 134 and infrared camera 132 to capture images from the same,adjacent, or otherwise similar vantage points, the trigonometricmathematical computations needed for the correlation step may besimplified or omitted altogether. In some embodiments, controller 320may use homography to project the visible light image and the infraredimage onto a plane corresponding to the cage floor or wall 110 oppositethe camera(s) to correlate the images. For example, the projected viewsmay be fused into a synthetic overhead view of the cage floor 115 orsynthetic side view of wall 110, where one or both cameras 132, 134chosen for certain pixel information in the synthetic view are selectedto reduce occlusions and maximize sensing resolution. Controller 140 mayaccomplish the correlation step.

As in step 460, the temperature of the at least one identified part ofthe animal may be determined. To accomplish this, pixels of the infraredimage corresponding to the coordinates of the at least one identifiedpart may be assessed. The color of each pixel represents an observedtemperature for that pixel. An overall observed temperature of a partmay be determined through evaluation of pixels corresponding to thatpart. In various embodiments, an average of all pixel valuescorresponding to the coordinates, an average of all pixel values afteroutlier values are omitted, all pixel values corresponding to a centralportion of the coordinates, a weighted average focused on the centerportion of the coordinates, and/or the like may be used to determine anoverall observed temperature for the part. For example, FIG. 7Dillustrates how pixels of an infrared image corresponding to thecoordinates of an eye may be assessed. In this example, as shown in FIG.7E, an average of all pixel values corresponding to the coordinates ofthe eye provides that the overall observed temperature of the eye is30.5° C. In another example, FIG. 7G illustrates how pixels of aninfrared image corresponding to the coordinates of a tail may beassessed. In this example, all pixel values corresponding to a centralportion of the coordinates may be used to determine an overall observedtemperature for the tail.

In some embodiments, the temperature values corresponding to the variouspixel colors may be calibrated, for example using a thermal reference150. This may be advantageous where, for example, the accuracy ofinfrared camera 132 may potentially be less than desirable. Further, useof a thermal reference 150 may permit use of more economical infraredcameras 132 that may otherwise be unsuitable due to their unreliableaccuracy. A thermal reference 150, for example as shown in FIG. 8, maymaintain a constant temperature within a high degree of accuracy. Forexample, thermal reference 150 may comprise a simple heater, athermostat, and a small metal block coated with a material of knownemissivity. In some embodiments, the emissivity may be similar to thatof mouse skin or another experimental animal. Additionally, the ambienttemperature of a cage, for example, as may be measured by air inletand/or air outlet temperature sensors, may provide a proxy temperaturereference indicative of the temperature of the bedding within cage 100.Thus, the bedding may be a ubiquitously visible reference for the coldend of the thermal spectrum. An infrared image may capture observedtemperatures for the bedding and/or thermal reference 150. Byassociating the pixels representing thermal reference 150 with theconstant accurate temperature of thermal reference 150 and/or byassociating the pixels representing the bedding with the proxy thermalreference temperature, the pixel-temperature scale may be calibrated.While at least one thermal reference may be used to compensate foroffset error (aka zero error), at least two thermal references may beneeded to compensate for gain error (aka span error).

Further, it may be advantageous to adjust the overall observedtemperature of a part to compensate for the angle and distance of thepart with respect to the infrared camera 132. This is because where apart is far from infrared camera 132 and/or does not directly faceinfrared camera 132, the overall observed temperature of the part mightnot accurately reflect that part's temperature. For example, in FIG. 6B,where the eyes of the mouse are substantially directly facing infraredcamera 132 and an average of all pixel values corresponding to thecoordinates are used to determine the overall observed temperature, theoverall observed temperature of each eye is approximately 33° C.; thisis because many more pixels are able to capture the “pure” temperatureof the eyes relative to pixels reflecting temperatures of areas adjacentto the eye, resulting in a more accurate observed overall temperature.By contrast, in FIGS. 7B, 7D, and 7E, where the eye of the same mouse issubstantially oblique to infrared camera 132 and the overall observedtemperature is determined the same way, the overall observed temperatureof the eyes is approximately 30.5° C.; this is because fewer pixels areable to capture the “pure” temperature of the eyes and relatively morepixels reflect temperatures of areas adjacent to the eye are included inthe average, resulting in a less accurate observed overall temperature.Similarly, where an animal is further away, each part may be representedby fewer pixels, which may result in a less accurate observed overalltemperature.

To adjust the overall observed temperature of a part to compensate forthe angle and distance of the part with respect to the infrared camera132, distance and angle may first be estimated as discussed above. Then,an appropriate adjustment to the overall observed temperature may bedetermined by using a lookup table indexed by angle and/or distance, orthe like. Such a lookup table may be experimentally created by capturinginfrared images of the same part of the same experimental animal from avariety of angles and/or distances with infrared camera 132 and derivingan appropriate adjustment for a plurality of suitable angles and/ordistance combinations. The lookup table may be created such that anadjusted final part temperature approximates the overall observedtemperature of the part from close-up distance and/or direct infraredimage capture.

Additionally, or alternatively, the distance and/or angle with respectto infrared camera 132 may be used to determine that a particularinfrared image is not suitable for determining a temperature. That is,an angle may be determined to be so oblique or a distance may bedetermined to be so large that an accurate part temperature cannot bedetermined with sufficient accuracy, even with adjustment as describedabove. For example, the second eye of the experimental animal depictedin FIGS. 7A and 7B (which is not the eye assessed in FIG. 7E), ispractically indistinguishable from the outline of the animal's body inthe infrared image of FIG. 7B. Here, the eye is positioned so obliquelyto the infrared camera 132 that its temperature may not be measured withreasonable accuracy. In such a circumstance, it may be desirable torepeat steps 410, 420, and 450, so that a more suitable infrared imagemay be used. Such a technique may prevent or reduce the likelihood ofinaccurate temperature measurements.

As in step 470, that least one physiological characteristic of theanimal may be determined.

As one example of determining a physiological characteristic, the coretemperature of an experimental animal may be determined. To determinethis, a part temperature of an eye of may be obtained. The parttemperature of the eye may have been adjusted for angle and/or distanceas discussed with respect to step 460. Then, a core temperature of theexperimental animal may be determined by using a lookup table indexed bythe eye temperature or the like. Alternatively, other parts of anexperimental animal, for example, exposed skin of a partially shaved orotherwise hairless rodent may be used.

Such a lookup table may be empirically built by manually taking thetemperature of an experimental animal, for example using a rectal probe,proximal in time with capturing an infrared image of the eye of the sameexperimental animal. The process may be repeated at least until enoughdisparate data points are gathered such that a core temperature/eyetemperature relationship curve may be estimated. In some embodiments,for example where a core temperature/eye temperature relationship curveis sought for a set of experimental animal clones, proximal in time maymean within seconds or minutes. However, in other embodiments, forexample, where the core temperature/eye temperature relationship curveis to be adjusted or confirmed for a specific experimental animal,proximal in time may mean within longer time ranges, such as the sameday.

As another example of determining a physiological characteristic, apresence or degree of swelling or inflammation may be determined. Forexample, data from an infrared image of the paw of an experimentalanimal can provide a reliable indicator of the magnitude of paw edema.This is because certain paw surface temperatures may vary in concertwith the level of swelling or inflammation in a particular region ofinterest. In turn, a measure of swelling or inflammation may be areliable indicator of experimentally induced arthritis. Sanchez, B. M.et al. (2008). “Use of a portable thermal imaging unit as a rapid,quantitative method of evaluating inflammation and experimentalarthritis.” Journal of Pharmacological and Toxicological Methods, 57(3),169-175, and Jasemian, Y. (2011). “Refinement of the Collagen InducedArthritis Model in Rats by Infrared Thermography.” BJMMR British Journalof Medicine and Medical Research, 1(4), 469-477), both of which areincorporated herein by reference in their entireties, provide examplesof well known techniques for measuring swelling, inflammation, andarthritis by evaluating data from infrared images.

Where an infrared image is captured from above, for example from aninfrared camera 132 within electronic monitor 200, it may be difficultor impossible to assess paw temperature from a resulting image becausethe paws are likely to be hidden. However, where an infrared image iscaptured from the side, for example through window 120 in wall 110, thepaws of an animal may be viewed from this side. A given level of pawswelling may manifest in different observed paw temperatures when aninfrared image captures the paw from the side as opposed to a head-onview. Thus, where paw temperatures are only available from a side view,it may be necessary to use an empirically determined lookup table or thelike to map side-view-observed paw temperatures to corresponding degreesof swelling or inflammation. Further, unwanted variances in observed pawtemperature may be reduced by using a reference temperature of theexperimental animal and accordingly adjusting the paw temperature or thelike. The experimental animal's eye temperature or derived coretemperature may be used as such a reference temperature of theexperimental animal instead of or in addition to using a temperatureobserved from a shaved or bald patch of the skin of the experimentalanimal, as suggested in the Jasemian reference.

As yet another example of determining a physiological characteristic, adegree of brown adipose tissue (aka brown fat) thermogenesis may bedetermined. Rodents may typically include brown adipose tissue depositsin the interscapular area, e.g. just behind their ears and between theirshoulder blades. Thermogenesis of such brown adipose tissue deposits maybe assessed by evaluating the temperature of skin adjacent to suchdeposits. Such temperature evaluation may be accomplished through use ofinfrared images to arrive at an observed part temperature, and a degreeof thermogenesis may be derived through the use empirically determinedlookup table or the like. Al-Noori, S. et al. “Brown Adipose TissueThermogenesis Does Not Explain the Intra-administration HyperthermicSign-reversal Induced by Serial Administrations of 60% Nitrous Oxide toRats.” Journal of Thermal Biology 60 (2016): 195-203, and Smriga, M. etal. “Use of Thermal Photography to Explore the Age-dependent Effect ofMonosodium Glutamate, NaCl and Glucose on Brown Adipose TissueThermogenesis.” Physiology & Behavior 71.3-4 (2000): 403-07, both ofwhich are incorporated herein by reference in their entireties, provideexamples of assessing brown adipose thermogenesis from temperature dataderived from infrared images.

It may be advantageous to provide experimental animals with a hairlessinterscapular region, which may be obtained by shaving or depilation insome embodiments or by providing a hairless experimental animal, toimprove accuracy of temperature measurements. Further, unwantedvariances in observed tumor temperature may be reduced by using areference temperature of the experimental animal and accordinglyadjusting the paw temperature or the like. The experimental animal's eyetemperature or derived core temperature may be used as such a referencetemperature of the experimental animal instead of or in addition tousing a temperature observed from a shaved or bald patch of skin.

As yet another example of determining a physiological characteristic, adegree of tumor vascularization may be determined. Tumor vascularizationmay be illustrative of tumor development, and measurement of superficialtemperatures above the tumor may provide an indirect measure of tumorvascularization. This is discussed in Faustino-Rocha, A. I. et al.“Ultrasonographic, Thermographic and Histologic Evaluation ofMNU-induced Mammary Tumors in Female Sprague-Dawley Rats.” Biomedicine &Pharmacotherapy 67.8 (2013): 771-76 and Poljak-Blazi, M. et al.“Specific Thermographic Changes During Walker 256 Carcinoma Development:Differential Infrared Imaging of Tumour, Inflammation and Haematoma.”Cancer Detection and Prevention 32.5-6 (2009): 431-36, both of which areincorporated herein by reference in their entireties.

A tumor may be grown in a location or part of an experimental animalthat may be readily viewable, for example, in an area just above thebase of the tail, in a leg, or on the top of the head, and located usingthe computer vision techniques disclosed above. A degree of tumorvascularization may be determined by evaluating the temperature of skinobserved at the tumor location, with higher temperatures beingassociated with more vascularization and lower temperatures beingassociated with less vascularization. Such temperature evaluation may beaccomplished through use of infrared images to arrive at an observedpart temperature, and a degree of tumor vascularization may be derivedthrough the use empirically determined lookup table or the like.

It may be advantageous to provide experimental animals with a hairlesstumor region, which may be obtained by shaving or depilation of the skincovering the tumor in some embodiments or by providing a hairlessexperimental animal, to improve accuracy of temperature measurements.Further, unwanted variances in observed tumor temperature may be reducedby using a reference temperature of the experimental animal andaccordingly adjusting the observed tumor temperature or the like. Theexperimental animal's eye temperature or derived core temperature may beused as such a reference temperature of the experimental animal insteadof or in addition to using a temperature observed from a shaved or baldpatch of skin.

As yet another example of determining a physiological characteristic, adegree of hair loss (e.g., alopecia) may be determined, as well as thelocations of such hair loss. In one example, the outline of theexperimental animal may be determined based on the visible light and/orinfrared images. Within this outline, areas of hair loss may bedetermined by quantifying areas of elevated temperature within theexperimental animal outline in the infrared image. Thus, it may not benecessary to determine the positions of individual parts of theexperimental animal in some embodiments. A degree of hair loss may bedetermined by, for example, calculating what portion of the experimentalanimal has a raised temperature; the calculation may account for thefact that certain portions of an experimental animal, for example theeyes and paws, are likely to have an elevated surface temperaturewithout being indicative of hair loss. In other embodiments, the outlinemay be processed to ensure that the eyes, paws, and/or other parts knownto have elevated temperatures are excised from the outline beforecalculation. In yet other embodiments, a specific area of hair loss maybe found, and then its size and/or position subsequently identified.

FIG. 9 is a flowchart of an exemplary embodiment of determining at leastone metabolic characteristic of an experimental animal in a livingspace. As discussed in Gordon, C. J. (1993). Temperature Regulation inLaboratory Rodents. Cambridge: Cambridge University Press, which isincorporated herein by reference in its entirety, a metabolicthermoneutral zone (TNZ) may be understood as a range of ambienttemperatures at which an animal's metabolic rate generally is at itslowest and at which regulatory changes in metabolic heat production orevaporative heat loss are generally not needed. A TNZ may be bound at alower end with a lower critical ambient temperature, below which ananimal will generally increase heat production. And, a TNZ may be boundat an upper end at an upper critical ambient temperature, above whichthe animal's metabolic rate increases above basal levels and evaporativeheat loss-mechanisms of the animal might activate.

As in step 910, the living space may be provided with a temperature nearor within the TNZ of the experimental animal being studied. As examples,the TNZ for various strains of mice, from lower critical ambienttemperature to upper critical ambient temperature, may be 30.6° C. toapproximately 34° C., 26° C. to 30° C., or 31° C. to 34° C. The TNZ forvarious strains of gerbils may be 30° C. to 35° C., 30° C. to 39° C.,28° C. to 32° C., or 32° C. to 34° C. The TNZ for various strains ofrats may be may be 29.2° C. to 31.0° C., 30° C. to 33° C., 28° C. toaround 33° C., 28° C. to 32° C., 28° C. to 34° C., 22° C. to 27° C., oraround 26.5° C.

In exemplary embodiments, the living space temperature to be providedmay be within a predefined range that is near or within the metabolicthermoneutral zone (TNZ) of the experimental animal. In variousexamples, this predefined range may include only temperatures that arewithin the metabolic thermoneutral zone of the animal or are within 2°C., 1° C. or 0.1° C. of the TNZ of the experimental animal. In otherexamples, the predefined range may include only temperatures that arewithin 2° C., 1° C., or 0.5° C. of the lower critical ambienttemperatures of the TNZ of the experimental animal. In yet otherexamples, the predefined range may be about 27° C. to about 28° C., 28°C. to about 29° C., or 29° C. to about 30° C. In yet other embodiments,the predefined range may be entirely above the upper critical ambienttemperature, but within 5° C., 4° C., 3° C., 2° C., or 1° C. of it. Inyet other embodiments, the predefined range may be entirely below thelower critical ambient temperature, but within 5° C., 4° C., 3° C., 2°C., or 1° C. of it.

As vivariums are generally kept cooler than a given experimentalanimals' TNZ, a desired living space temperature may be provided by aheater or heating element, for example, within cage 100 or electronicmonitor 200 that operates in conjunction with a thermostat. Airconditioning or another cooling apparatus may optionally be included ifthe temperature becomes too warm. In other embodiments, air at thedesired living space temperature may be vented in. Although a smallerpredefined range of temperatures may provide more accurate experimentaldata than a wider range or predefined temperatures, as ranges getsmaller it may become more difficult or require more expensive equipmentand maintenance to sustain a living space temperature within thepredefined range.

As in step 920, a chemical compound and/or other stimulus may beprovided to the experimental animal. Such compound may include apharmaceutical, a possible or putative pharmaceuticals, prototypes ofpharmaceuticals, or compounds intended to affect mechanisms similar towhat related pharmaceuticals might affect. The stimulus may be social,physical, relating to nutrition, relating to odor, relating to mating,relating to hydration, and/or the like. Because, in exemplaryembodiments, the experimental animal's metabolism is to be checked inlater steps, this optional step is included in the flowchart to providean example of when a chemical and/or stimulus might be provided in orderto assess the metabolic affect of such chemical and/or stimulus. Forexample, pharmaceuticals that increase metabolism are generally desiredto promote weight loss; compound candidates for such drugs may beassessed via this method.

As in step 930, the living space temperature is confirmed. In someembodiments, the ambient temperature of a cage, for example, may bemeasured and confirmed by air inlet and/or air outlet temperaturesensors. In other embodiments, the cage may include a digitalthermometer, whose output is provided to controller 140, or an uncoupledthermometer that may be captured in a visible light image and read whenthe image is processed. In some embodiments, an infrared image of theexperimental animal, animal bedding, and a thermal reference 150 with atemperature within the predefined range may be captured with infraredcamera 132. Here, the living space temperature may be confirmed bycomparing the color of the thermal reference 150 to the color of thebedding in the infrared image. With reference to the calibrationdiscussion above, the bedding may be a ubiquitously visible referencefor temperature of the cage. Multiple thermal references 150 at varioustemperatures may be provided in cage 100 for calibration purposes, asdiscussed above, or to visually establish the predefined range in theinfrared image. In yet other embodiments, step 930 may not be a stepdistinct from step 910. For example, proper operation of a thermostatmay serve as confirmation that the living space temperature is withinthe predefined range.

As in step 950, the core temperature of the experimental animal may bedetermined. The core temperature may be determined based on the observedtemperature of an eye of the experimental animal in an infrared image,as discussed above. In step 950, an infrared image, perhaps along with avisible light image, may be captured if it was not already capturedduring step 930. In other embodiments, the core temperature of theanimal may be determined by assessing the color of a portion of hairlessskin that is included in an infrared image. Or, the core temperature maybe manually taken with a thermometer. In yet other embodiments, asdiscussed below, this step may be excluded entirely. That is, especiallywhere the temperature of the living space is confirmed, the coretemperature of the experimental animal may be assumed to be normal ornear normal.

As in step 960, the tail temperature of the experimental animal may bedetermined. As described above, such temperature may be determined byprocessing of an infrared image of the animal, and, in some embodimentsa visible light image. In step 960, an infrared image, perhaps alongwith a visible light image, may be captured if it was not alreadycaptured during either of steps 930 and 950. Alternatively oradditionally to determining the tail temperature, a paw or foottemperature may be determined.

As in step 970, a metabolic characteristic of the experimental animalmay be determined. Mice, rats, and other rodents control heat lossthrough adjustments in vasomotor tone (PVMT) of, for example, theirtails or feet. For example, at typical room temperature (e.g., 20°C.-25° C.) or when a mouse is cold, blood flow through the tail of themouse is restricted to prevent heat loss. In such circumstances, thetemperature of the tail of the mouse may be, for example, 15° C.-25° C.,measurably lower than its core temperature. However, when the mouse istoo warm the tail is vasodilated to allow blood to flow through the tailat higher rates, and subsequently dissipate heat through thesubstantially hairless tail surface. In such circumstances, thetemperature of the tail of the mouse may approach or even meet its coretemperature. Thus, PVMT and consequently a metabolic rate of anexperimental animal may be indicated by the experimental animal's tailtemperature.

Notably, different portions of the tail may be at different temperaturesat any given instant. For example, because some heat dissipates from theflowing blood by the time it reaches the tip of the tail, the tip of thetail is likely to be cooler than the base of the tail. Thus, moreprecise data may be gathered by consistently taking the tail temperaturefrom the same portion or portions of the tail. For example, the tailtemperature may be an average of all tail temperatures, all tailtemperatures but outliers, the tip section of the tail, the middlesection of the tail, the base section of the tail, and/or the like.

In one embodiment, a determination of metabolic rate increase and/or ofmetabolic rate may be determined by taking the difference (aka delta)between the experimental animal's core temperature and its tailtemperature. If the animal's metabolic rate is normal, the differencemay be expected to be at its maximum. The difference between the coreand tail temperatures will become smaller and smaller as the metabolismof the animal increases. Then, a metabolic rate may be determined byusing a lookup table indexed by difference between the core and tailtemperatures, and perhaps the ambient temperature of the living space,or the like. Such a lookup table may be empirically created by measuringthe metabolic rate of the animal and simultaneously or nearsimultaneously obtaining tail, core, and/or ambient temperatures, forexample via an infrared image capture.

In this embodiment, it may not be necessary to maintain and/or confirm apredetermined temperature range as in steps 910 and 930. For example,the living space temperature may be permitted to stay at or near roomtemperature. Here, because the animal's core temperature is included aspart of the metabolic characteristic determination calculation, anymeasured increase in metabolic is activity is likely to be accurate.However, by providing a living space temperature at or around theexperimental animal's TNZ, especially near its lower critical ambienttemperature, a modest increase in metabolism is more likely to result inan measurably increased tail temperature and increases in tailtemperatures are likely to occur more rapidly.

In another embodiment, step 950 may be omitted and a normal coretemperature may be assumed. Here, a metabolic rate may be determined byusing a lookup table indexed by tail temperature, and perhaps theambient temperature of the living space, or the like. Such a lookuptable may be empirically created by measuring the metabolic rate of theanimal and simultaneously or near simultaneously obtaining tail and/orambient temperatures, for example via an infrared image capture.

It is contemplated that portions of the metabolic characteristicdetermining process (e.g., steps 930, 950, 960, and 970) may becontinuously repeated after the compound and/or stimulus is administeredto determine how long a metabolic response of the experimental animaltakes to begin, how long it takes to finish, and/or the manner in whichit progresses. Such a technique may deliver richer datasets.

It is contemplated further that, for some studies, the metaboliccharacteristic determining process may be repeated multiple times at aplurality of predefined temperatures in and around the TNZ of theanimal. Such serial measurements may provide more robust datasets fromwhich the metabolic effects of particular compounds and/or stimuli maybe more thoroughly evaluated.

Alternatively or additionally to determining a metabolic characteristicbased on the tail temperature, a paw or foot temperature may be used ina similar fashion.

Although the foregoing embodiments have been described in detail by wayof illustration and example for purposes of clarity of understanding, itwill be readily apparent to those of ordinary skill in the art in lightof the description herein that certain changes and modifications may bemade thereto without departing from the spirit or scope of the appendedclaims. It is also to be understood that the terminology used herein isfor the purpose of describing particular aspects only, and is notintended to be limiting, since the scope of the present invention willbe limited only by the appended claims.

It is noted that, as used herein and in the appended claims, thesingular forms “a”, “an”, and “the” include plural referents unless thecontext clearly dictates otherwise. It is further noted that the claimsmay be drafted to exclude any optional element. As such, this statementis intended to serve as antecedent basis for use of such exclusiveterminology as “solely,” “only,” and the like in connection with therecitation of claim elements, or use of a “negative” limitation. As willbe apparent to those of ordinary skill in the art upon reading thisdisclosure, each of the individual aspects described and illustratedherein has discrete components and features which may be readilyseparated from or combined with the features of any of the other severalaspects without departing from the scope or spirit of the disclosure.Any recited method can be carried out in the order of events recited orin any other order that is logically possible. Accordingly, thepreceding merely provides illustrative examples. It will be appreciatedthat those of ordinary skill in the art will be able to devise variousarrangements which, although not explicitly described or shown herein,embody the principles of the disclosure and are included within itsspirit and scope.

Furthermore, all examples and conditional language recited herein areprincipally intended to aid the reader in understanding the principlesof the invention and the concepts contributed by the inventors tofurthering the art, and are to be construed without limitation to suchspecifically recited examples and conditions. Moreover, all statementsherein reciting principles and aspects of the invention, as well asspecific examples thereof, are intended to encompass both structural andfunctional equivalents thereof. Additionally, it is intended that suchequivalents include both currently known equivalents and equivalentsdeveloped in the future, i.e., any elements developed that perform thesame function, regardless of structure. The scope of the presentinvention, therefore, is not intended to be limited to the exemplaryconfigurations shown and described herein.

In this specification, various embodiments have been described withreference to the accompanying drawings. It will be apparent, however,that various other modifications and changes may be made thereto andadditional embodiments may be implemented without departing from thebroader scope of the claims that follow. The specification and drawingsare accordingly to be regarded in an illustrative rather thanrestrictive sense.

We claim:
 1. A method for electronically determining a metaboliccharacteristic of an experimental animal in a living space, the methodcomprising: confirming that a temperature in a living space is within apredefined range that consists of temperatures near or within ametabolic thermoneutral zone of the experimental animal; capturing atleast one infrared image of at least one experimental animal in a bandof infrared radiation that is within the range of from about 3 μm toabout 14 μm in wavelength; identifying at least one data set of the atleast one infrared image that corresponds to a tail of the experimentalanimal; processing the at least one data set of the at least oneinfrared image to evaluate a temperature of the tail of the experimentalanimal; and determining the metabolic characteristic based at least inpart on the evaluated tail temperature.
 2. The method of claim 1,wherein the predefined range consists of temperatures within about 2° C.of the metabolic thermoneutral zone of the experimental animal.
 3. Themethod of claim 2, wherein the predefined range consists of temperatureswithin about 1° C. of the metabolic thermoneutral zone of theexperimental animal.
 4. The method of claim 3, wherein the predefinedrange consists of temperatures within about 0.1° C. of the metabolicthermoneutral zone of the experimental animal.
 5. The method of claim 4,wherein the predefined range consists of temperatures within themetabolic thermoneutral zone of the experimental animal.
 6. The methodof claim 1, wherein the predefined range consists of about 27° C. toabout 28° C.
 7. The method of claim 1, wherein the predefined rangeconsists of about 28° C. to about 29° C.
 8. The method of claim 1,wherein the predefined range consists of about 29° C. to about 30° C. 9.The method of claim 1, wherein the predefined range consists oftemperatures within about 1° C. of a lower critical ambient temperatureof the metabolic thermoneutral zone of the experimental animal.
 10. Themethod of claim 1, wherein the predefined range consists of temperatureswithin about 0.5° C. of a lower critical ambient temperature of themetabolic thermoneutral zone of the experimental animal.
 11. The methodof claim 1, wherein identifying at least one data set of the at leastone infrared image that corresponds to a tail of the experimental animalfurther comprises: determining a position of the tail within the livingspace; and correlating the position of the tail with the at least oneinfrared image.
 12. The method of claim 11, wherein determining aposition of the tail within the living space further comprises:capturing at least one visible image of the at least one experimentalanimal; and processing the at least one visible image using one or morecomputer vision techniques to determine the position of the tail. 13.The method of claim 1, further comprising heating the living space tocause the temperature in the living space to be within the predefinedrange.
 14. The method of claim 1, wherein the living space furtherincludes a temperature reference point and wherein confirming thetemperature of the living space further comprises: determining aposition of a temperature reference point within the living space;capturing at least one infrared image of the temperature reference pointin a band of infrared radiation that is within the range of from about 3μm to about 14 μm in wavelength; and correlating the determined positionof the temperature reference point with the at least one infrared imageto determine the temperature of the living space.
 15. The method ofclaim 1, further comprising: measuring a core temperature of theexperimental animal; and calculating a difference between the coretemperature and the tail temperature, wherein determining the metaboliccharacteristic based at least in part on the tail temperature furthercomprises determining the metabolic characteristic based at least inpart on the calculated difference between the core temperature and thetail temperature.
 16. The method of claim 15, wherein measuring the coretemperature of the experimental animal further comprises measuring aneye temperature of an eye of the experimental animal.
 17. The method ofclaim 16, wherein measuring the eye temperature of an eye of theexperimental animal further comprises: determining a position of the eyeof the experimental animal within the living space; and correlating thedetermined position of the eye with the at least one infrared image todetermine the eye temperature.
 18. The method of claim 17, whereindetermining the position of the eye within the living space furthercomprises: capturing at least one visible image of the at least oneexperimental animal; and processing the at least one visible image usingone or more computer vision techniques to determine the position of theeye.
 19. The method of claim 1, further comprising: administering achemical compound to the experimental animal.
 20. A method forelectronically determining a metabolic characteristic of an experimentalanimal in a living space, the method comprising: capturing at least oneinfrared image of at least one experimental animal in a band of infraredradiation that is within the range of from about 3 μm to about 14 μm inwavelength; measuring a core temperature of the experimental animalusing the at least one infrared image; measuring a temperature of a tailof the experimental animal using the at least one infrared image;calculating a difference between the core temperature and the tailtemperature; and determining the metabolic characteristic based at leastin part on the calculated difference.
 21. The method of claim 20,further comprising maintaining a temperature of the living space withina predefined range that consists of temperatures near or within ametabolic thermoneutral zone of the experimental animal.